总结并分析了新疆地区几回750 kV输电线路覆冰跳闸原因和整改措施.结合事故调研,利用ANSYS软件对均匀覆冰、三段覆冰、线性覆冰和高悬挂端覆冰工况进行了有限元分析,结果表明,线路覆冰跳闸主要由地线非均匀覆冰导致导、地线局部静态距离不足而引起;比较非均匀覆冰中的三段覆冰、线性覆冰与高悬挂端覆冰,高悬挂端覆冰对弧垂最低点偏移的影响最大,且随覆冰长度的增加,导、地线静态接近距离存在极小值.通过工程实例计算发现,地线高悬挂端覆冰下导地线最小接近距离小于规程规范限定的最小静态距离,并能导致放电跳闸,工程设计中应重视此种情况下的间距校验.

输电线覆冰在升温、自然风或人为外力作用下会发生覆冰整档或一档内部分位置脱冰,引起输电线跳跃,导致导线相间或导地线间闪络、线路跳闸、断股断线以及输电塔失稳倒塌等事故,严重威胁电力系统安全.参照实际750 kV输电线路工程,建立连续档分裂导线有限元模型,分析档数、档距、高差、覆冰厚度、风速、脱冰率和绝缘子串长度等因素对导线均匀和不均匀脱冰跳跃高度的影响;讨论均匀和不均匀两种脱冰方式下导线脱冰跳跃高度之间的联系,定义不均匀脱冰时发生脱冰的导线长度为换算档距;对比现有导线冰跳高度计算公式的准确性,提出不均匀脱冰跳跃高度系数.结果表明:当脱冰荷载相同时,不均匀脱冰引起的脱冰跳跃高度更大;不均匀脱冰时冰跳高度与换算档距下完全脱冰的冰跳高度存在一定比例关系;建立了导线均匀脱冰和不均匀脱冰跳跃高度计算公式,所提均匀脱冰跳跃高度计算公式的最大相对误差为11.8％,不均匀脱冰跳跃高度计算公式相对误差大于10％的结果仅占结果总数的13.2％,计算精度较高,有助于线路设计时确定相地或相间安全间隙.

Unbalanced tension in the overhead power lines under non-uniform ice is important for the design of towers. Based on the constant conductor length and numerical iteration methods, a numerical calculation method to determine the unbalanced tension under non-uniform accreted ice in one span for both the single-span and multi-span sections has been developed. Meanwhile, the horizontal tension and sag distribution calculated by the numerical calculation method are in good agreement with the finite element analysis (FEA) model established in the ANSYS software and the field situation. The responses of the unbalance tension and the maximum relative displacement of the conductor under different parameters, including span length, ice length, ice thickness, number of spans, and elevation difference were investigated. Also, the application of a numerical calculation method to practical line situations was discussed. The results show that the non-uniform ice clearance reaches the flashover condition first compared with the static clearance and the dynamic clearance under different span lengths, ice thicknesses, and voltage levels, especially in the low voltage level power lines.

采用简支梁理论与"等线长法"模型,提供了一种求解架空线路单端覆冰下不平衡张力的方法,与现有技术相比,提出了连续档单端覆冰下档距变化量Δlk的计算公式.通过与ANSYS软件数值仿真结果对比,该文方法能准确计算出电线单端覆冰情况下的不平衡张力及形态分布.文章还分析了覆冰故障实例,运用该文方法的计算结果与现场情况基本吻合,且导线脱冰、地线单端覆冰下导地线最小接近距离小于现有规范要求值,在大高差的线路设计中,应校验此种情况下的间距.该文计算方法既能满足工程精度的要求,又能形成简便实用的计算程序,适用于工程实际计算,用于指导塔头的设计,提高线路抗冰能力.

近年来新疆地区极端天气现象多次发生,尤其在天山山脉地区,输电线路覆冰致灾问题愈发严重,给电网的安全稳定运行带来了巨大挑战.为此,分析了750 kV输电线路覆冰跳闸原因及相应的整改措施,介绍了输电线路覆冰与脱冰工况下的间隙校距公式,并结合具体工程实例进行计算.分析计算结果表明:在翻越山峰的爬坡地带,导线脱冰、地线高悬挂端覆冰下的导、地线最小接近距离小于现行规范限定的最小静态距离,并能达到放电跳闸条件,因此,在工程设计中应重视此种情况下的间距校验.

为求解同走廊同电压等级交流线路的并行间距,考虑架空线路并行时的电磁环境、风偏下的安全间隙及施工控制距离,得出多回交流线路并行间距的经验公式,并分析公式在理论和工程运用中的正确性和适用性.结果表明,并行间距由地面工频电场强度或电气安全距离控制,并可按经验公式确定.工程运用中,经验公式在各电压等级常规杆塔规划下均适用,在个别大档距下,需校核塔位异步布置时的电气安全距离,同塔双回路并行间距可借鉴此经验公式,110～330 kV电压等级线路并行间距可根据实际情况缩小.

总结并分析了国内外初伸长的预测方法及处理措施,得出了各种计算结果不同的原因.国际大电网预测公式考虑了应力和永久伸长之间的互相循环影响,预测结果和蠕变试验结果接近,可满足工程设计要求.由于规范考虑初伸长求架线应力时,应变值剔除了架线过程中已拉出的塑性伸长,因此规程规范对初伸长的规定均较小.架线时间4～48 h内,架线过程释放的伸长量在14％～24％之间,为提高初伸长预估值的准确性,需根据架线时间调整初伸长或安装降温值.

为推进玻璃纤维增强树脂基复合材料(GFRP)在特高压交流工程的应用,依托锡盟一胜利特高压工程,针对上字型复合横担塔提出了电气、结构设计方案;开展了电场和结构有限元仿真分析;开展并通过了电气验证试验、真型塔结构试验以及构件拉压疲劳试验;提出了复合横担塔的工程施工和验收方案以及运维方案.通过经济性对比分析得出,与常规酒杯型角钢塔相比,复合横担塔可使呼高降低8m、走廊宽度减少21.2 m、工程本体造价节约4％.

1 前言 随着国家“西部开发”、“西电东送”战略的实施,河西走廊通道内密集分布着电力线路、铁路、高速公路、油气管线等各种设施,廊道拥挤,已建的哈密-郑州±800kV直流线路、正在建设的准东-华东送出±1100kV、规划建设准东-成都±1 100kV直流输电线路工程及多条750kV、330kV也将从此通过,因此有利用已有的330kV通道,采用1100kV与330kV同塔多回输电技术是解决河西走廊电力通道问题的有效手段.

Selection of the conductor is important in the design of power transmission lines.This paper demonstrates possibilities of using quadri-split conductors in 750 kV transmission lines,including comprehensive analysis and comparison of its electrical properties,mechanical performance and economic performance.The study results show that in the areas of lower altitude and smaller corona loss,the quadri-split conductors with the adequate aluminum cross-section meet the electromagnetic environment limits,reduce the preliminary investment,and their long-term operation economy are equivalent to those of the six-split conductors,therefore help substantially to reduce the project cost.

The application situations of diameter-extended conductor for UHVAC transmission line projects were presented. Based on 1 000 kV Ximeng-Nanjing UHVAC transmission line project, the electrical characteristics, mechanical performances and the economic features of diameter-extended conductor and conventional conductors were compared. The results show that the diameter-extended conductor not only meets the electromagnetic environment requirements, but also can effectively reduce the project investment for UHVAC transmission line projects, under the precondition of satisfying the transmission capacity, which has great practical significance for the construction of environmentally friendly and resource-saving UHVAC transmission lines.